This invention relates generally to the field of antenna switching circuitry. More particularly, this invention relates to an antenna switching circuit arrangement for multi-mode transceivers including a full duplex mode of operation.
Antenna switches are circuits which are commonly used in radio communication devices to direct RF signals along their proper signal paths during receive and transmit functions of the radio communication device. In devices such as cellular telephones and other full duplex transceivers, transmitter and receiver circuits can be active simultaneously while sharing the same antenna. In such transceivers, the transmitted power from the transmitter power amplifier should generally be isolated with a high level of attenuation from the receiver circuitry in order to prevent the transmitted power from damaging the receiver circuitry. This is commonly implemented using a duplexer to isolate the signal paths. Those having ordinary skill in the art will appreciate that a duplexer is normally a device made up of two series band pass filtering devices with a center tap, but any other component configuration which provides the functionality of a duplexer can be used equivalently.
The advent of multi-mode transceivers substantially complicates the design requirements for antenna switching circuits while marketplace factors demand long battery life, low cost and high levels of performance. In some designs, it is particularly important to provide high linearity to effect a high adjacent channel coupled power ratio (ACCPR), even under high voltage standing wave ratio (VSWR) conditions.
It is desirable to provide an antenna switching circuit which can be used in a variety of applications thereby increasing economies of manufacturing scale while providing the required functionality across multiple configurations of multi-mode transceivers. For example, Motorola, Inc., the Assignee of the present invention, manufactures a series of radios conforming to the iDEN (Integrated Digital Enhanced Network) specification which provides two way xe2x80x9cpush to talkxe2x80x9d type simplex communication in combination with AMPS (Advanced Mobile Phone Service) cellular telephone service. AMPS cellular telephone service is the conventional analog cellular in the United States. Other multi-mode transceiver configurations which can share this common design include iDEN/CDMA (Code Division Multiple Access), TDMA (Time Division Multiple Access)/AMPS, TETRA (Trans-European Trunk Radio) AMPS, and TETRA/CDMA. Other multi-mode transceiver configurations may also be able to adapt use of the antenna switching circuitry disclosed herein.